Cell free factors mediate immune function as well as the expression of an inflammatory response. Since the expression of many of these factors is increased in the cells from elderly donors the biologic implication of this finding are very important. Resistance to and severity of infectious diseases in the elderly may be due to a change in the control of cellular function. The mechanism for the increase in the cells from old donors appears to be due to an increase in a subset of memory T cells which synthesize and release these factors. The expression of receptors for the factors as well as an analysis of their ability to generate cellular signals in the cells from young and old mice will provide evidence for the biologic role of these factors in the older individuals.